From 564bc37de50075e03ccfba5dc894ae25804ef3ce Mon Sep 17 00:00:00 2001
From: Rachit Kumar Verma <155641117+rachitvrma@users.noreply.github.com>
Date: Sat, 11 Jul 2026 16:19:33 +0530
Subject: [PATCH] kitty: fix diff.conf being generated regardless of user
 config

'cfg.diffConfig' is an implicit submodule with sub-options that carry
their own defaults, so it never actually equals `{ }` - the previous
`cfg.diffConfig != { }` check was always true. This caused
'kitty/diff.conf' to be written (and clobber any existing unmanaged file)
even when the user configured nothing under `programs.kitty.diffConfig`.
---
 modules/programs/kitty.nix                    |  2 +-
 tests/modules/programs/kitty/default.nix      |  1 +
 .../kitty/example-diffConfig-expected.conf    |  6 ++++++
 .../programs/kitty/example-diffConfig.nix     | 21 +++++++++++++++++++
 4 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100644 tests/modules/programs/kitty/example-diffConfig-expected.conf
 create mode 100644 tests/modules/programs/kitty/example-diffConfig.nix

diff --git a/modules/programs/kitty.nix b/modules/programs/kitty.nix
index e2a75fc7d6..9484485581 100644
--- a/modules/programs/kitty.nix
+++ b/modules/programs/kitty.nix
@@ -433,7 +433,7 @@ in
       '';
     };
 
-    xdg.configFile."kitty/diff.conf" = mkIf (cfg.diffConfig != { }) {
+    xdg.configFile."kitty/diff.conf" = mkIf (cfg.diffConfig.extraConfig != "") {
       text = ''
         # Generated by Home Manager
         # See https://sw.kovidgoyal.net/kitty/kittens/diff/
diff --git a/tests/modules/programs/kitty/default.nix b/tests/modules/programs/kitty/default.nix
index 789650367a..1c0fce4157 100644
--- a/tests/modules/programs/kitty/default.nix
+++ b/tests/modules/programs/kitty/default.nix
@@ -5,4 +5,5 @@
   kitty-example-mkOrder = ./example-mkOrder.nix;
   kitty-example-quickAccessTerminalConfig = ./example-quickAccessTerminalConfig.nix;
   kitty-auto-theme-files = ./auto-theme-files.nix;
+  kitty-example-diffConfig = ./example-diffConfig.nix;
 }
diff --git a/tests/modules/programs/kitty/example-diffConfig-expected.conf b/tests/modules/programs/kitty/example-diffConfig-expected.conf
new file mode 100644
index 0000000000..6ff2ebcc16
--- /dev/null
+++ b/tests/modules/programs/kitty/example-diffConfig-expected.conf
@@ -0,0 +1,6 @@
+# Generated by Home Manager
+# See https://sw.kovidgoyal.net/kitty/kittens/diff/
+diff_cmd auto
+
+map j scroll_by 1
+
diff --git a/tests/modules/programs/kitty/example-diffConfig.nix b/tests/modules/programs/kitty/example-diffConfig.nix
new file mode 100644
index 0000000000..e2040a76b7
--- /dev/null
+++ b/tests/modules/programs/kitty/example-diffConfig.nix
@@ -0,0 +1,21 @@
+{
+  config = {
+    programs.kitty = {
+      enable = true;
+
+      diffConfig = {
+        settings.diff_cmd = "auto";
+        keybindings = {
+          "j" = "scroll_by 1";
+        };
+      };
+    };
+
+    nmt.script = ''
+      assertFileExists home-files/.config/kitty/diff.conf
+      assertFileContent \
+        home-files/.config/kitty/diff.conf \
+        ${./example-diffConfig-expected.conf}
+    '';
+  };
+}